1. Technical Field
The invention relates to the field of identification markings. More particularly, the invention is a method and composition of matter for forming a tamper-indicating identification coating on electronic parts.
2. Background Art
Electronic goods are prevalent in modern civilization and range from simple toys to high technology computers and other devices. Most electronic goods contain electronic parts that are soldered onto printed circuit cards or boards. Electronic parts range from simple, inexpensive devices to complex, costly integrated circuit chips. As with most goods, electronic goods and parts generally bear a warranty for specified amounts of time, ranging from months to years. The range of time depends on the failure rate and expense of the parts as well as other business considerations such as the quality to be associated with the goods and parts.
Typically, all the parts on a given card bear the same warranty rather than individual parts on the card having separate warranties or warranty periods. Accordingly, if a card becomes defective within the warranty period the entire card is replaced. At times, the part that fails on the card is the most expensive part, such as an integrated circuit chip. When a card that is outside its warranty period becomes defective due to failure of its most expensive part, there is an opportunity and motivation for fraud on the manufacturer of the card. Such cards may bear little or no value depending on the relative cost of the remaining non-defective parts. Typically, cards bear some sort of label or means for tracking the card to determine whether the card is inside or outside of its warranty period. However, a card is made up of multiple small parts that cannot be tracked individually without significant effort and expense. Accordingly, while cards can be identified as outside a warranty, individual parts generally cannot.
Due to the circumstances described above, it is possible for a defective part from an out-of-warranty card to be removed and used to replace the same type of non-defective part on an in-warranty card. The in-warranty card with the out-of-warranty defective part is then sent away for repair or replacement. At times, resoldering of the defective part gives the solder an appearance that differs enough from the original solder for the manufacturer to detect tampering, however, techniques are available to avoid that detection. Unless the fraudulent act is discovered, the manufacturer will pay to repair or replace the card whereas, otherwise, the manufacturer would gain revenue from the sale of a new card. This type of warranty fraud is relatively pervasive throughout the electronics industry.
Turning to FIG. 2, one technique manufacturers are currently using to prevent warranty fraud includes a self-destruct label 200. Self-destruct label 200 is simply a strip of material coated with an adhesive wherein one end of label 200 is adhered to the electronic part (e.g. integrated circuit chip 100) and the other end is adhered to a circuit card 110. Label 200 is sufficiently fragile that, if an attempt is made to remove label 200, it will appear damaged. By this means, tampering is detected, however, the labels are relatively expensive and some labels can be counterfeited. Also, some labels may give a false positive indication of tampering because the label usually spans a gap 210 between chip 100 and card 110. Because of its fragility, the portion of label 200 that spans gap 210 and is not adhered either to chip 100 or card 110 may become damaged just from handling the card 110.
Another current technique involves thermochromic materials, that is, coatings that change color in response to being exposed to a given temperature. Specifically, the techniques for resoldering a defective part onto an in-warranty card expose the part to heat. If the part is coated with a thermochronic material that changes color when the part is exposed to the heat associated with resoldering, then tampering can be detected. However, once the color change occurs, it will be visibly apparent and the part can simply be recoated with any material that restores the original color.
Thus, it can be seen from the above discussion that it would be an improvement in the art to provide an inexpensive, reliable means for detecting the presence of out-of-warranty electronic parts on in-warranty circuit cards. Without a means of detecting when parts have been replaced on a circuit card, the computer and electronics industry will continue to suffer extensive revenue loss due to warranty fraud.